Dec 022012

Find out more about IP addresses (IPv4 and IPv6) using the Python module IPy:

#!/usr/bin/env python

from IPy import IP

ip_s = raw_input('Please enter an IP address or range: ')
    i = IP(ip_s)
except ValueError:
    print('Could not understand your input %s. Exiting.' % ip_s)
    from sys import exit

print('I understood: %s' % i)
print('This is an IPv%d address.' % i.version())

#if i._prefixlen != 32: # a network
    net = len(i) > 1 # a network
    size = len(i)
    net = True
    size = "large"
if net:
    print('net: %s' %
    print('netmask: %s' % i.netmask())
    print('broadcast: %s' % i.broadcast())
    print('reverse notation of net address: %s' % i.reverseNames()[0])
    print('size of subnet: %s' % size)
else: # a single IP
    print('reverse notation: %s' % i.reverseNames()[0])

if i.version() == 6:
    print('normal notation: %s' % i.strNormal())
    print('full size notation: %s' % i.strFullsize())
print('hexadecimal notation: %s' % i.strHex())
print('string notation of binary value: %s' % i.strBin())
print('type of ip: %s' % i.iptype())
if i.get_mac(): print('found possible mac address: %s' % i.get_mac())
Mar 172012

This is a really compact and cheap router to take with you to hotels etc. to secure your internet access via VPN or redistribute a network.

The Hardware

You can get some information on the used hardware from my /proc/cpuinfo, /proc/meminfo and dmesg.

I put some photos I made of the PCB online on this PicasaWeb album.

More details to be found in OpenWrt’s wiki page on the router.

Aug 222011


The RFC 2217 standardizes the transmission of serial connection data via Ethernet, allowing to change remote serial port parameters (such as speed, parity, stop bits) over TCP using NVT (Network Virtual Terminal).


Connection between your serial device and the Ethernet

Jun 262011


cd ~/Downloads
curl -C - -O
open synergy-1.4.5-MacOSX107-x86_64.dmg
cd /Volumes/Synergy/
cp -r /Applications/

Start the server:

synergys -f --config ~/synergy.conf

where synergy.conf is:

# sample synergy configuration file
# comments begin with the # character and continue to the end of line.
# comments may appear anywhere the syntax permits.

section: screens

section: links
            right = lion

            left  = seagull


section: aliases

Connect the client

synergyc -f --name seagull 192.168.seagull.ip
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Jan 122011

Go to System → Preferences → Keyboard Shortcuts and set the shortcut for Hide all normal windows and set focus to desktop to something sane like Alt + D

update 2011-07-13: This happened again when I used Ubuntu 11.04 inside a NX session on a Mac OS X host computer. :(


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Jul 032010

Installation on Ubuntu:

sudo aptitude install ipwatchd-gnotify

if configured correctly (true by default) it will show you graphical warnings for IP conflicts as well as create log entries in /var/log/syslog (check for log messages containing ipwatchd).

Advanced configuration options are described and have to be set in the file/etc/ipwatchd.conf. This could be running a custom script as soon as an IP conflict is being detected for example.

When you detect an IP conflict, it might be an illegitimate attempt to take over your IP. So you want to tell the network who’s the real owner of that IP: this is done using arping and described in my blog post React to IP Takeover.

Jun 112010

You can use tcpdump to debug TCP/IP connections.

How it works

1st console run tcpdump:

philipp@lion:~$ sudo tcpdump -i lo
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 96 bytes
09:55:05.968006 IP lion > lion: ICMP echo request, id 5745, seq 1, length 64
09:55:05.968025 IP lion > lion: ICMP echo reply, id 5745, seq 1, length 64
09:55:06.967003 IP lion > lion: ICMP echo request, id 5745, seq 2, length 64
09:55:06.967024 IP lion > lion: ICMP echo reply, id 5745, seq 2, length 64
8 packets captured
16 packets received by filter
0 packets dropped by kernel

2nd console start any network activity (in this case a ping to localhost):

May 262010

When someone has taken your IP, react!

Set your IP to the correct one (belonging to you):

sudo ifconfig eth0 netmask

and run arping to get the IP back on your side:

sudo arping -U -c 3 -I eth0
sudo arping -A -c 3 -I eth0

Also have a look at my ipwatchd blog post on the ipwatch daemon, which can detect IP conflicts.


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Apr 222010

Warning: my experience with gmailfs was not excellent! It was a bit slow and you always risk to lose data you stored on that account.

based on IMAP:
(it used to be but this was based on the Webinterface and that changed often)

gmailfs works with FUSE. So make sure Fuse is installed and works:

Add user philipp to group fuse, install the python-fuse Ubuntu package and get the gmailfs code:

sudo usermod -aG fuse philipp
sudo aptitude install python-fuse
cd ~/Downloads
git clone git://

you also need from libgmail. See

Mar 232010

An easier solution just by setting a line in the configuration of the ssd daemon can be found in the blog post Chroot SFTP users.

sudo aptitude install scponly


sudo -s
cd /usr/share/doc/scponly/setup_chroot
chmod +x

this adds the user etc…

sudo chmod u+s /usr/sbin/scponlyc

to not display the message of the day (motd) for raxo when logging in via shell and allow other users to put files in the incoming folder:

sudo -s
cd /home/scpuser
touch .hushlogin
chmod 777 incoming
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